CLADOENDESIS OF EPHEMEROPTERA

ABC

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Acanthametropus/fg1

(Panephemeroptera Euephemeroptera Euplectoptera Anteritorna pm.Tridentiseta
 - Acanthametropus/fg1)

Nomen hierarchicum: Acanthametropus/fg1 [f:1963; g:1948] (incl. Analetris)

In circumscription fits:

— subfam. Acanthametropodinae: Hubbard 1982: 50

— fam. Acanthametropodidae: McCafferty & Wang 1994b: 214

— Acanthametropus/fg1: Kluge 2004: 88


References. Edmunds & Koss 1972: *; – Edmunds & Jensen & Berner 1976: * *; – Kluge & Studemann & Landolt & Gonser 1995: * *; – Kluge 2004: * * *.


Autapomorphies of Acanthametropus/fg1.

(1) Mouth apparatus is specialized for carnivorism, both Analetris and Acanthametropus/fg2 pray on chironomid larvae. Labrum with wide median incision. Asymmetry of mandibles is lost; each mandible is shortened perpendicular to axis of articulation and elongated along this axis, incisor and kinetodontium are stout, prostheca is lost, mola lacks grater. Superlinguae are vestigial (Kluge & al.1995: Fig.23-30). Maxillae are stout, biting; apical setae are absent; canines and dentisetae are situated in one plane, only two canines are present, first and second dentisetae are canine-like, third dentiseta can be vestigial or lost (Kluge 2004: Fig.23:B) [see Plesiomorphies of Tridentiseta]. 2nd (penultimate) segment of labial palp is widened (Kluge 2004: Fig.23:C).

(2) Larval legs are specialized [see (3) and (6)], fore and middle legs differ from hind ones: femora of fore and hind legs are widened, claw of hind leg is much longer than claws of fore and middle legs (Tshernova 1948: Fig.3).

(3) On each leg tibia is shortened, tarsus is elongate; on imaginal and subimaginal middle and hind legs 1st tarsal segment is longer than tibia.

(4) Sterna with median projections: in larva projection is present at least on prosternum and mesosternum, in imago – on prosternum (Kluge 2004: Fig.23:D-E) (in larval Acanthametropus/fg2 projections are present not only on thorax, but on abdomen also).

(5) Each tergalius I–VII consists of 3 lamellae: dorsal lamella is initial one, and 2 ventral lamellae represent 2 parts of expanded anal-proximal lobe bent down. In Analetris each of these 3 lobes has integral margins (Edmunds & Koss 1972: Fig.4), while in Acanthametropus/fg2 these lobes are strongly dissected and their projections are tangled (Kluge 2004: Fig.23:A). Anal rib is lost, thus only costal rib is present on initial (dorsal) lamella.

(6) Entire larval body is dorsoventrally flattened and widened, claws are strongly elongate [see (2)] (Tshernova 1948: Fig.1-3; Burks 1953: Fig.312; Edmunds & Koss 1972: Fig.1). Non-unique apomorphy – the same in some other specialized psammophils, such as Ametropus and Pseudiron.

(7) Larval abdominal terga and sterna bear stout scales – i.e. flattened setae (whose sockets are not widened, unlike scales of Turbanoculata) and lack denticles on posterior margin (Lehmkuhl 1976: Fig.13). Non-unique character.

Plesiomorphies of Acanthametropus/fg1. Larva retains features of primary swimming siphlonuroid specialization: legs are able to stretch posteriorly [in spite of specialization – see (2), (3), (6)]; abdomen is large, able to make undulate swimming movements; caudalii are not long, paracercus is well-developed, primary swimming setae are dense, secondary swimming setae are absent. Larval head is hypognathous. Labial palp [see (1)] is 3-segmented. Larval (and adult) patella-tibial suture [on short tibia – see (3)] is developed on middle and hind legs only. Larval claws [see (2)] are slightly curved, without denticles.

In imago and subimago: Mesonotal suture is nearly transverse (at least in Acanthametropus/fg2). Anterior paracoxal suture is complete (Kluge 2004: Fig.23:E) (unlike Rallidens and some Bidentiseta). Furcasternal protuberances are contiguous (Kluge 2004: Fig.23:E) (unlike Amphinotic groups of Tridentiseta and some others – see Index of characters [2.2.23]). Subimaginal lateral pigmented area of mesonotum is small, stretches along lateroparapsidal suture and does not occupy sublateroscutum (Kluge 2004: Fig.23:F) (see Index of characters [2.2.14]). In cubital field of fore wing several (3–8) veins go from CuA to basitornal margin or anastomose and can be partly substituted by intercalaries [see Anteritorna (1)]; hind wing is well-developed, as long as 0.45–0.5 of fore wing length (Kluge 2004: Fig.24:A-B). Imaginal and subimaginal tarsi are 5-segmented, 1st segment [long – see (3)] is fused with tibia. Claws are ephemeropteroid [exception can be made by male fore legs only – see below, Acanthametropus/fg2 (6)]. Imaginal and subimaginal paracercus is subequal to cerci.

Size. Fore wing length 12–20 mm.

Age and distribution. Recently distributed in Amphipacific Sector of Holarctic: Eastern Palaearctic and Nearctic. Reporthed from Baltic amber (see Analetris).


The taxon Acanthametropus/fg1 is divided into:

1. Analetris

2. Acanthametropus/fg2